Validation Of QTLs For Two Chromosome Segment Substitution Lines For Bolting Traits In Brassica Rapa

Chromosome segment substitution lines(CSSLs)are one of the most powerful tools for fine mapping of quantitative trait loci(QTL)and evaluation of gene interaction in theoretical studies.In order to facilitate the analysis of complex quantitative traits in Brassica rapa breeding,molecular marker technology was often used in assisted selection breeding.In this study,a CSSL population consisting of 120 lines of Chinese cabbage was constructed by multiple generation backcrossing and self-crossing after crossing between the recipient parent’Rc Br’and the donor parent ’08A061’.Five CSSLs were selected for phenotypic identification of bolting-related traits,ultimately,two of them were selected to construct NIL-F2 population for validating and analysing the QTLs of bolting-related traits in B.rapa.The results of the research are as follows:1.In the advanced population,Five CSSLs were selected for further phenotypic identification of bolting-related traits.QTLs associated with bolting were all detected in the linkage groups of A02,A04,A06,A07,A08 and A10.According to the seed harvest of offspring,the NIL-F2 population of multi-segment CSSLs was constructed and named17AW007 and 17AW008 respectively.2.In 17AW007 population,QTLs associated with bolting were located in A04,A0 7 and A10 linkage groups by using the software Windows QTL Cartographer 2.5 and composite interval mapping,which explained the phenotypic variation ranged from 7.86 to 34.26%.Among these QTLs,the LOD value of A04 linkage group was 15.64 and the locus was 91.3c M,explaining 34.26% of phenotypic variation.the QTL was named q BI-4-1;the three QTLs located in 17AW008 population were between the marker Br ID10995-BOE993 in A06 linkage group,and explained the phenotypic variation ranged from 4.6 to 9.7%.3.Six candidate genes related to flowering were detected in the QTL candidate intervals of A04,A06,A07 and A10 linkage groups.According to the physical location of the corresponding molecular markers in the Chinese cabbage database,a candidate gene Bra040434 related to flowering was detected in the locus of A04 linkage group,and two genes related to flowering were detected in the locus of A07 linkage group,Bra004007 and Bra003913,respectively.The function of AT1G71800 gene was similar to that of FLC gene in Arabidopsis thaliana,and two Flowering-related genes were detected in A06 linkage region,Bra009970 and Bra004361,respectively.Bra009970 gene had similar function with AT3G05120,AT3G63010 and AT5G27320 in Arabidopsis thaliana,which regulated flower organogenesis and participated in scab.A candidate gene Bra009491 related to flowering was detected in the A10 linkage group mapping region,which was involved in triglyceride metabolism.